This invention relates to the production of aminothiophenols, e.g.,para-aminothiophenol, and their derivatives, such as N-acyl-aminothiophenols, e.g., N-acetyl-para-aminothiophenol.
Aminothiophenols and their derivatives have various actual and potential uses in commerce. For example, aminothiophenols such as para-aminothiophenol are important intermediates for the synthesis of pharmaceuticals such as antiarthritics, steroid derivatives, and anti-malarials, and are also used as photograph antifogging agents.
U.S. Pat. No. 4,524,217, issued Jun. 18, 1985 to K. G. Davenport and C. B. Hilton, and assigned to the same assignee as this application, teaches the preparation of N-acyl-hydroxy aromatic amines, e.g., N-acetyl-paraaminophenol (APAP), by reacting a hydroxy aromatic ketone, e.g., 4-hydroxyacetophenone (4-HAP), with hydroxylamine or a hydroxylamine salt, to form the oxime of the ketone, and subjecting the oxime to a Beckmann rearrangement in the presence of a catalyst to form the N-acyl-hydroxy aromatic amine. The patent also discloses the preparation of hydroxy aromatic esters such as phenyl acetate or the Friedel-Crafts acylation of phenols using hydrogen fluoride as catalyst and cites several references disclosing these reactions. The entire disclosure of this patent is incorporated by reference.
Auwers et al, Chemische Berichte 58, 36-51 (1925), show the Beckmann rearrangement of a large number of oximes of aromatic ketones, most of which are substituted acetophenones.
Ganboa et al, Synthetic Communications 13, 941-944 (1983), show the production of acetanilide from acetophenone by refluxing in a solution of hydroxylamine hydrochloride.
None of the three preceding references discloses any method for the preparation of an N-acyl aromatic amine from an aromatic ketone by oxime formation and Beckmann rearrangement, where the aromatic groups have a sulfur-containing ring substituent such as mercapto or thiocarbamoyl.
Newman et al, Journal of Organic Chemistry 31, 3980-3984 (1966), teach the formation of O-aryl dialkylthiocarbamates by reaction of a phenol with a dialkyl thiocarbamoyl chloride, and the pyrolytic rearrangement of O-aryl dialkylthiocarbamates to S-aryl dialkylthiocarbamates. Specifically disclosed in Table I is the pyrolytic rearrangement of O-4-acetophenyl to S-4-acetophenyl dimethylthiocarbamate.
Newman et al, U.S. Pat. No. 3,476,791, disclose a process similar to that disclosed in the article cited in the preceding paragraph and was issued to patentees who are the same as the authors of such article. Example 14 of the patent shows the preparation of p-acetylphenyl dimethylthiolcarbamate from p-acetylphenyl dimethylthioncarbamate.
Kwart et al, Journal of Organic Chemistry, 31, 410-413 (1966), show the vapor phase pyrolytic rearrangement of various diaryl thioncarbonates to O,S-diaryl thiolcarbonates and of various O-aryl dialkylthioncarbamates to S-aryl dialkylthiolcarbaeates.
Copending application Ser. No. 875,158 filed Jun. 17, 1986 by Davenport and assigned to the same assignee as this application discloses a method of producing aminothiophenols and their derivatives, including a somewhat different sequence of reactions than that of the instant application.